1. Field of the Invention
The present invention relates to a rotation force transmission mechanism and a rotation force transmitter which is built in the same.
2. Description of the Related Art
With regard to a rotation mechanism in which a rotation force of a rotation driving source such as a stepping motor is transmitted to a rotated member via a rotation force transmitter, there is a problem that vibrations and torque fluctuations (rotation unevenness) generated by the rotation driving source is transmitted to the rotated member. In the related art, for the purpose of solving this problem, a load which has a flywheel effect is mounted on a rotation driving force or such a load is built in a rotation force transmission member, whereby vibrations and torque fluctuations transmitted to a rotated member are suppressed. However, in the case of the related art methods, the weight of a rotation force transmission mechanism becomes heavy.
FIG. 6 is a view showing a related art rotation force transmission mechanism, and FIG. 7 is a side view taken along an arrow A of FIG. 6. In a rotation force transmission mechanism 1, vibrations and torque fluctuations generated by a rotation driving source 3 are transmitted via a first driving transmission belt 4 to a junction flywheel 2 which is a rotation force transmitter, and transmitted via a pulley portion 5 and a hub portion 6 of the junction flywheel 2 and a second driving transmission belt 7 to a pulley portion 9 of a driven flywheel 8 which is a rotated member. The junction flywheel 2 having a heavy weight suppresses vibrations and torque fluctuations. However, according to the related art, the junction flywheel has a heavy weight and therefore cannot abruptly start rotating or abruptly stop rotating.
Further, other related art mechanisms are disclosed in Japanese Unexamined Patent Publications JP-A 6-249321 (1994) and JP-A 2001-665 (2001). In JP-A 6-249321, between an inside perimeter of an annular pulley portion and an outside perimeter of a hub portion, a vibration-absorbing elastic body made of an elastic material is connected. The vibration-absorbing elastic body prevents that vibrations and torque fluctuations are transmitted from the pulley portion to the hub portion (or from the hub portion to the pulley portion). However, according to the related art, selection of a material of the vibration-absorbing elastic body is difficult, the number of components increases, and because the vibration-absorbing elastic body, the hub portion and the pulley portion are made of different materials, respectively, it is difficult to join the vibration-absorbing elastic body and the hub portion and join the vibration-absorbing elastic body and the pulley portion, with the result that a cost becomes high.
Further, in JP-A 2001-665, an inside perimeter of an annular pulley portion and an outside perimeter of a hub portion are connected by a plurality of spokes which are placed at predetermined spaces in the perimeter direction, whereby vibrations and torque fluctuations are suppressed. Although, in this related art, the spokes become elastically deformed along the perimeter direction of the pulley portion and thereby vibrations in the perimeter direction are suppressed, vibrations in the radial direction cannot be suppressed.